Dkk-1 (Dickkopf or Dickkopf-1) is a secreted inhibitor of the Wnt/canonical signaling pathway which mediates a variety of cellular processes. Wnt proteins are extracellular signaling molecules that initiate activation of the canonical pathway by binding low-density lipoprotein receptor-related protein 5&6 (LRP5/6) coreceptors, triggering a cascade of events that stabilize beta-catenin. Wnts mediate osteoblast development and cell-to-cell interactions during embryogenesis, and are also responsible for regulating bone mass in adults during normal bone remodeling processes. Wnts are also found to be expressed during the stationary phase of the cell cycle and are thought to control expansion of bone marrow stromal cells preventing overpopulation in marrow.